Hello all. Haven't posted in a long time but I wanted to drop some information while I had a few moments.

So early this year I started a quest to find the key fob frequency and see if I could find a way to replace the fob. Well, unfortunately life got in the way of my extracurricular projects and projects such as this were sidelined.

Here is what I found so far though.

1. The key fobs operate on the 125 KHZ frequency. This is not the same as modern key fobs that typically operate in the 315, 390 and 433 MHZ frequencies. This means that a modern key fob cannot be repurposed or reprogrammed for use. The 125 KHZ frequency was/is used by the passive RFID tag system.

2. The key fob is an active transmitter. This means that passive RFID systems cannot be used.

This is where I had to put the project on hold. I have not found a suitable replacement for our key fob system, yet. I don't have equipment that can receive in the 125 KHZ range to look at the modulation and code being passed from FOB to car. I was researching what would be needed when I got sidelined.

If anyone has equipment or knowledge to assist, it would be appreciated as my free time is not as much as I would like it to be.

Hope everyone had a good summer.

 

*FobIt was 109 shipped. Her info is*C4fob@yahoo.com

just a quik email away

 

Thanks. I have two fobs that work and I am not looking for a new one or a rebuilt one.

The original discussion and intent was/is to decode the system and see what is out there as new tech to replace the fobs that is more readily available and cheaper or replace the system completely if desired.

Active proximity 125 KHZ RFID chips can be bought for 2-3 dollars each. Cheaper if you buy in lots of 100. If these chips can be programmed with the correct "coding" then a FOB that can be purchased for less than 5 bucks is much better than one for 110 bucks in my opinion.

I don't currently own the equipment for this (perhaps next year) and I don't have the time to spend on this project right now (again perhaps next year). Once I have both, then the decoding and programming shouldn't be much of an issue.

In the early 90's, security wasn't first and foremost, so I'm sure the encryption is minuscule at best if not then non-existant all together. If I had a receiver hooked to an Android phone that would tune to 125 KHZ then I am pretty sure any PKE equipped C4 could be unlocked in a matter of seconds just like any analog code garage door can be opened.

So as I said before, if anyone here has this equipment or additional knowledge of the system, such as modulation type, encryption type, polling order and timing, then this project can be completed quickly.

 

If I am not mistakeing she had something to do with the design of the system and knows more than most. From what I have seen 0n the forum.

 

Why don't you just ask Bree?

 

I see this is an old thread but on a positive note, technology has had nearly another decade to evolve. I'm a recent owner of a 95 C4 with no fobs and I'm determined to replicate the signal somehow or another. It has to work! If anyone had an update please share, otherwise I'm going to enlist my electrical engineering buddy at NASA to help me pick up where you left off. Thank you for posting your research!

 

This is an old one. I don't have the C4 anymore so I can't try what I am about to tell you. You could try a flipper zero and see what that can do. https://flipperzero.one/

Although without an original fob i am not sure how far you will get. Best of luck.

 

Ordered a flipper zero and an excruciatingly expensive fob off eBay. Fingers crossed I can figure these things out and come up with a solution for the C4 community. If there are any guinea pigs who want to participate in a custom fob experiment with me lmk 😎

 

I would be interested.